整理した

src/server/api/stream/messaging.ts

@@ -1,9 +1,11 @@
 import * as websocket from 'websocket';
 import * as redis from 'redis';
 import read from '../common/read-messaging-message';
+import { ParsedUrlQuery } from 'querystring';
 
 export default function(request: websocket.request, connection: websocket.connection, subscriber: redis.RedisClient, user: any): void {
-	const otherparty = request.resourceURL.query.otherparty;
+	const q = request.resourceURL.query as ParsedUrlQuery;
+	const otherparty = q.otherparty as string;
 
 	// Subscribe messaging stream
 	subscriber.subscribe(`misskey:messaging-stream:${user._id}-${otherparty}`);